I was at a relatively smallish (maybe a few hundred people) tech event in Phoenix the first week in March. There had been some consideration to canceling but they went ahead. They were cleaning surfaces, doing elbow bumps instead of handshakes but no masks, distancing, etc.

I was supposed to head on to another fairly small event in Tahoe the next week but the Thursday before, they canceled it. Which TBH seemed excessive to me at the time. (Though CA was starting to see an increase in cases.) I got home, did some shopping before everything went crazy but about a week later offices were closing, etc.